1. Field of the Invention
This invention concerns the construction of a swing arm to which a ski of a snowmobile is attached. In particular, this invention encompasses a swing arm construction for the front suspension of a snowmobile that facilitates the passage of snow and other elements underneath the swing arm.
2. Description of Related Prior Art
FIG. 6 illustrates a conventional snowmobile 10, which is manufactured by Bombardier Inc. of Montreal, Quebec, Canada. While only the left side of the snowmobile 10 is illustrated, those skilled in the art would readily appreciate that the right side is essentially a mirror image thereof.
The snowmobile 10 is constructed with a frame 12 powered by a motor 14. The motor 14 is preferably an internal combustion engine, which may be one of either the two-stroke or four-stroke variety. Handlebars 16 are disposed above and to the rear of the motor 14. The handlebars 16 operatively connect to two skis 18, 20 disposed at the front of the snowmobile 10. When turned by the handlebars 16, the skis 18, 20 turn the snowmobile 10 in the desired direction.
The skis 18, 20 are suspended from a front suspension system 23. The front suspension system 23 includes, among other components, two straight swing arms 24, one disposed on either side of the snowmobile 10. The swing arms 24 connect to shock absorbers 26.
The motor 14 operatively connects to an endless track 30 at the rear of the snowmobile 10 beneath a tunnel of the frame 12. The endless track 30 propels the snowmobile 10 forward (or backward, as the case may be).
As illustrated in FIG. 7, a spindle 34 connects to the left ski 18 through a bridge 36. The bridge 36 typically is an elongated U-shaped structure with a bottom portion 38 connected to the ski 18. The spindle 34 and ski 18 are attached to the snowmobile front suspension system 23 via a spindle holder 56, which is attached to a forward portion of the swing arm 24. A rear portion of the swing arm 24 connects to the frame 12 via a pivot collar 58 and pin 60. Connecting the swing arm 24 to the frame 12 of the snowmobile 10 in this manner serves at least two functions. First, the pivot collar 58 permits the swing arm 24 to pivot upwardly and downwardly, which allows the ski 18 to move up and down as the snowmobile 10 traverses the ground. The pivot collar 58 also holds the ski 18 in a generally fixed longitudinal position relative to the frame 12 so that the ski 18 does not move rearwardly during operation of the snowmobile 10.
A bracket 62 attaches to the forward portion of the swing arm 24 at the location of the spindle holder 56. The bracket 62 operatively connects to the frame 12 via upper and lower radius arm assemblies 64 and 66. The upper and lower radius arm assemblies 64, 66 serve at least two functions. First, they permit the swing arm 24 to pivot about the pivot collar 58. This, in turn, permits the spindle 34 and ski 18 to move up and down relative to the frame 12. Second, they keep the spindle 34 and ski 18 in a generally fixed lateral position with respect to a centerline 68 of the snowmobile 10. In other words, the radius arm assemblies 64, 66 prevent the ski 18 from collapsing laterally inwardly or outwardly during operation.
To cushion the forces experienced by the ski 18 as it traverses the ground (so that the forces are not transmitted to the rider), the shock absorber 26 extends between the bracket 62 and the frame 12. The shock absorber 26 ensures that the frame 12 remains disposed above the ground. It also dampens any shocks encountered when the snowmobile 10 encounters rough terrain.
The swing arm 24 is normally constructed of sheet metal that is bent to form a straight hollow channel. Tubular swing arms constructed from metals and carbon fibers are also known. One common feature of all swing arms is their straight-line construction from the front of the swing arm to the rear of the swing arm. Because the front end of the straight swing arm 24 is disposed at the spindle 34 and is therefore close to the ground, an intermediate portion of the swing arm 24 has a low ground clearance that creates an obstruction for passing snow and other elements. When traveling in powder snow, the skis 18, 20 tend to sink down into the snow and further reduce or eliminate the ground clearance of the swing arm 24.
It is, therefore, an aspect of one or more embodiments of the present invention to provide an improved snowmobile swing arm construction.
According to another aspect of one or more embodiments of the present invention, a swing arm includes upward curves, steps, or angles that improve the swing arm""s ground clearance.
According to another aspect of one or more embodiments of the present invention, a swing arm assembly is provided with a rear portion adapted to pivotally connect to a snowmobile about a swing arm pivot axis, a forward portion having a bottommost point, and an intermediate portion extending between the front and rear portions and defining a lower edge. A portion of the lower edge is disposed above a line extending between the bottommost point and the swing arm pivot axis.
The portion of the lower edge is spaced from the line by a distance that is preferably at least 2 cm, is more preferably at least 4 cm, and is even more preferably at least 6 cm.
The lower edge may be curved or angled. The lower edge may alternatively form a step.
The swing arm assembly may also include a pivot collar attached to the rear portion such that the pivot collar defines the swing arm pivot axis.
The swing arm assembly may also include a spindle holder attached to the forward portion. The spindle holder is constructed and arranged to pivotally receive a ski
The swing arm assembly may also include a bracket attached to the spindle holder. The bracket is adapted to receive at least one radius rod to attach the swing arm to a snowmobile.
The swing arm assembly may be combined with a snowmobile that includes a frame pivotally connected to the rear portion of the swing arm, a straddle-type seat supported by the frame, a steering ski supported by the front portion of the swing arm, and an endless track supported by the frame.
According to another aspect of one or more embodiments of the present invention, a swing arm assembly is provided with a rear portion adapted to pivotally connect to a snowmobile about a swing arm pivot axis, a forward portion having an upper front tip, and an intermediate portion extending between the front and rear portions and defining a lower edge. A portion of the lower edge is disposed above a line extending between the upper front tip and the swing arm pivot axis.
Additional and/or alternative aspects, features, and objects of the embodiments of the present invention will become apparent from the following drawings and detailed description.